Oxyluminescent light sources and processes of making same



E. T. CLINE Get. 31, T967 OXYLUMINESCENT LIGHT S OURCES AND PROCESSES OFMAKING SAME Original Filed June 11, 1965 CLAMP-0N VALVE POROUS SUBSTRATEIHPREGNATED TRANSPARENT PLASTIC ENVELOPE EDGES HEAT SEALED ITHOXYLUMIRESCERT MATERIAL PLASTIC ENVELOPE Fr L E" POROUS SUBSTRATE IFZPREGNATED WITH OXYLUPEINESCENT MATERIAL HEAT SEA TRANSPARENT PLASTICTUBE SERUET STOPPER W i w L D a 1 E M T R A N T: i G A 5 E M A R m P iT. v m M .v T S I A E m m H I 00 U H. U L A. 5 VI .H M l M R T EXT/WI wSERUM STOPPER INVENT OR EDWARD T. C LINE ATTORNEY United States Patent3,350,553 OXYLUMINESCENT LIGHT SOURCES AND PROCESSES OF MAKING SAD/mEdward T. Cline, Wilmington, Del., assignor to E. I. du Pont de Nemoursand Company, Wilmington, Del., a corporation of Delaware Continuation ofapplication Ser. No. 463,398, June 11, 1965. This application Aug. 5,1965, Ser. No. 477,614

18 Claims. (Cl. 240-225) This application is a continuation of mycopending application, Ser. No. 463,398, filed June 11, 1965, itself acontinuation-in-part of my copending application Ser. No. 397,038, filedSept. 16, 1964, both now abandoned.

This invention relates to extended light sources as opposed to pointsources. More particularly, it relates to such light sources based onoxyluminescent materials.

Extended light sources are useful in various applications, e.g., infacilitating rescue operations for isolated groups on land, for downedaircraft and personnel at sea or for personnel overboard at sea.

A novel and useful extended light source is provided by the presentinvention. This invention is an oxyluminescent article comprising asheet-like or rope-like porous substrate impregnated with a tetrakis(disubstituted-amino) ethylene oxyluminescent material enclosed in aflexible plastic envelope or tube, at least one portion of which,generally one whole side of the envelope or the whole tube, istranslucent and preferably transparent, and the assembly being fittedwith at least one means for admitting air, e.g., a valve, port, tearstrip, puncturable section, or the like, to the oxyluminescent materialin controlled amounts when desired.

The invention will be understood in more detail from the remainder ofthis specification and from the essentially self-explanatory drawings inwhich:

FIG. 1 discloses a view of a transparent panel serving as an extendedlight source of the invention in which two rectangular sheets oftransparent plastic material are heatsealed at the edges and providedwith valves to form a transparent envelope surrounding a spacercomprising a porous substrate impregnated with oxyluminescent materialto which air can be admitted through the valves;

FIG. 2 represents a section along line 22 of FIG. 1 showing the poroussubstrate; and

FIG. 3 represents a section of an alternative embodiment of theinvention (see, e.g., Example XVI below) in which a porous substrateimpregnated with oxyluminescent material is inserted within atransparent plastic tube and the ends of the tube are sealed OE Withhypodermicpuncturable serum stoppers.

Preferably (1) the enclosing envelope or tube is constructed of a toughplastic which has low oxygen permeability and high resistance to theoxyluminescent material and its oxidation products, (2) the poroussubstrate, if not rough or uneven, is provided with a course, open-mesh,net-like structure to prevent intimate contact with the enclosingenvelope or tube, (3) the side of the envelope opposite the translucentor transparent side being provided with a light-reflective layer, e.g.,an aluminum coating or foil, or the tube being provided with a lightreflector which may be flat or hemicylindrical or of parabolic crosssection, (4) the oxyluminescent material in the porous substrate is atetrakis(disubstituted-amino)-ethylene of the formula wherein the Rs arethe same or diflerent and are monovalent alkyl or cycloalkyl of up tocarbon atoms, di-

9 prepared in a variety of ways.

3,35,553 Patented Get. 31, 1967 valent alkylene joined to the other Rattached to the same nitrogen to form a 35 membered monoaza heterocycle,and divalent alkylene joined to an R attached to a second nitrogen toform a 37 membered diaza heterocycle, and (5) the oxyluminescentmaterial is in an inert liquid or semisolid carrier.

The oxyluminescent articles of this invention have varying degrees ofshelf stability, depending on the oxygen permeability of the particularenvelope or tube employed. Thus, articles prepared with enclosures oflow oxygen permeability, e.g., enclosures of polyvinyl fluoride, retaintheir ability to luminesce when air is admitted after storage forperiods of up to four months or more in air at normal room temperatures.Articles can be stored for even longer times if they are protected evenmore carefully from the ingress of oxygen or air, e.g., by storing themin an inert atmosphere, e.g., an atmosphere of nitrogen, in a closedmetal or glass container. When enclosures of higher oxygen permeabilityare employed, e.g., envelopes or tubes made of polyethylene of 2-4 milsthickness, the slow permeability of oxygen through this material causesthe oxyluminescent material in the porous substrate to luminesce quitestrongly for a period of a few hours, due to oxygen penetrating theenclosing plastic. The luminescene then gradually decreases to a veryfeeble glow at the end of several days. When articles constructed withenclosures of low oxygen permeability are activated by admitting air tothe inner impregnated layer, they give very good luminescence forrelatively long periods of time. Thus, panels of this type 2-4 feetsquare are visible under clear weather conditions for distances of 2-4miles. Even relatively small tubes one foot long x a" diameter can beseen from distances of feet or more.

The oxyluminescent articles of this invention can be In these variousmethods, a critical factor is that the impregnation of the poroussubstrate with the oxyluminescent material must be carried out under asoxygen-free conditions as possible.

A convenient method of preparing panel-type articles comprises placing asheet or layer of a porous substrate that is inert to the oxyluminescentmaterial between two sheets of flexible plastic, at least one of whichpermits passage of light through it, i.e., is translucent ortransparent, of a size slightly larger than the porous substrate. Priorto sealing the plastic sheets, an opening is made near the edge of oneof them and a valve, port, or other means for permitting access to theinner portion of the panel is inserted. The edges of the outer plasticsheets then are sealed, for example, by heating, if the plastic layersare capable of being heat sealed or by the use of an adhesive if theyare not heat scalable.

A convenient method for preparing tubular articles of this inventioncomprises passing a string or cord through a length of plastic tubing,e.g., by means of a jet of compressed air or nitrogen, then attachingone end of the cord to the end of a narrow strip, rope, multiple strandsor sleeving of porous substrate and pulling the substrate into thetubing. As in the case of panels, the porous substrate is inert to theoxyluminescent material with which it is to be impregnated. The poroussubstrate must have a cross sectional area such that it does notcompletely fill the plastic tube in order that air can circulate throughthe tube when light is desired. The tubular article also is providedwith a valve, port, or other means for permitting access to the innerportion of the tube.

The valve or port enables the removal of air from the panel or tube bysuccessive evacuation and flushing the interior with an inert gas, e.g.,nitrogen. The successive evacuation and flushing steps are repeated asmany times as necessary to insure substantially complete removal of airfrom the interior of the enclosure. The oxyluminescent material, i.e.,the tetrakis(disubstituted-amino)ethylene,

3 preferably dissolved in an inert solvent, e.g., mineral oil, paraffinwax or polyisobutylene, is introduced through the valve or port and thevalve is then closed, or a sealing strip is placed over the opening.

Alternatively, the outer plastic enclosures can be out too long in onedimension. After the original sealing, the flushing and filling can beperformed by inserting hypodermic needles in the excess length. Finally,another seal can be made inside the needle hole areas and the excesslength trimmed off.

In preparing the oxyluminescent panels, it is preferable to insertbetween the porous substrate and the transparent face of the envelope(or between the porous substrate and bothsides of the envelope ifdesired) a coarse, open-mesh or net-like structure, e.g., nylon netting,as a spacer. The spacer prevents the porous substrate when wet withoxyluminescent material from adhering to the outer plastic film. Thispermits air to circulate more uniformly between the substrate and theouter plastic layers, with the result that when air is admitted to startthe luminescence of the panel, a more uniform and intense light emissionoccurs.

A spacer can also be placed between the porous substrate and the wallsof the flexible plastic tube to allow air to circulate more readilybetween the substrate and the walls of the tube. However, in the case oftubular light sources, the spacer is not as important as in the case oflarge panels.

The plastic envelope surrounding the porous substrate can be made ofsheetsof a single plastic or it can be made of sheets of a plastichaving a coating of the same or different polymer to provide loweroxygen permeability, or to impart heat sealability or other property tothe film. Furthermore, the enclosing envelope can be made of a compositesheet of plastic consisting of two or more coated or uncoated plasticfilms laminated together. The upper and lower outer layers of theenvelope can be made of the same or dififerent plastic films. However,all components of a laminated structure on at least one side of theporous substrate must be transparent or translucent. Similarly, thetubular articles of this invention can be made of plastic tubes having acoating, either :inside or outside, or both, of the same or differentpolymer to provide thesame desired properties as in the case of panels.

A preferred embodiment of the articles of this invention comprisestheuse of a transparent plastic outer layer on both sides of the poroussubstrate with a thin layer of light-reflective material, e.g., aluminumfoil, cemented to the outside of the bottom layer of the envelope ortube. Alternatively, aluminum or other metal can be vacuum deposited onthe outside of the lower 'plastic sheet and protected by a coating oranother plastic. Tubes can be provided with external, fiat, or shapedlight reflectors as discussed above. The use of such a light-reflectivelayer produces a surprising increase in the amount of light visible fromthe transparent side of the article. The results obtained in a typicalcase are given in Example IX.

Other embodiments of the panels'of this invention include the use of apressure-sensitive, -or tacky, adhesive on the back of the panel or onone-side of the tube to facilitate its attachment to any desired objector surface. Alternatively, snaps can be afiixed to the panels or tubesto permit attachment to another object.

The oxyluminescent materials particularly useful in the articles of thisinvention include the tetrakis(disubstituted-amino)ethylenes of theformula wherein the Rs havethe meanings defined hereinbefore. Specificoxyluminescent compounds of this type includetetrakis(dimethylamino)ethylene, tetrakis(N pyrrolidinyl)ethylene,1,1,3,3 tetramethyl-A '-bi(imidazolidine), -l,1,3,3' tetraethyl-Abi(imidazolidine), l,l-diethyl- 4 3,3'-dimethyl A bi(imidazolidine),l,1,3,3' tetramethyl A bi(hexahydropyrimidine), andtetrakis(dimethylaminomethyleneamino ethylene.

The tetrakis(dimethylamino)ethylene can be prepared by reaction ofdimethylamine with chlorotrifluoroethylene as described in I. Am. Chem.Soc. 72, 3646 (1950). The other tetrakis(disubstituted-amino)ethylenesof the above general formula and the bis(disubstituted-amino)hydrocarbyloxymethanes intermediate thereto can be prepared by reactionof the requisite basic secondary amine and any amide acetal, i.e., anydisubstituted-aminodi'hydrocarbyloxymethane in accord with the followingstoichiometry:

wherein the Rs, which can be alike or different, are monovalent alkyl orcycloalkyl radicals, generally of no more than eight carbons each, whichcan be together joined (in a divalent radical) to form with theintervening nitrogen a heterocycle of from three to seven ring members;the R's, which can also be alike or different, or together joined, aremonovalent (or divalent) alkyl, aryl, aralkyl, alkaryl, or cycloalkylradicals, generally of no more than eight carbons each, and whentogether joined, form with the two oxygens and intervening carbon 211,3-dioxaheterocycle of from five to seven ring members; and the R"s,which can also be alike or different or together joined, are monovalent(or divalent) alkyl or cycloalkyl hydrocarbon or oxaand/orazahydrocarbon radicals of no more than eight carbons each, eachnitrogen carrying no more than one methyl group and, in the case of thedivalent radicals, no more than 6- carbons per divalent radical. In anyevent, when the two R"s are together joined, they form with theindicated amine nitrogen a monoazacarbocycle, an oxaazacarbocycle, or adiazacarbocycle of from three to seven ring members. This process isdescribed in greater detail in US. Pat. 3,239,- 519.

As indicated previously, the oxyluminescent materials used in the panelsof this invention are conveniently used with an inert, nonquenchingsolvent or carrier, i.e., a material which does not extinguish theoxyluminescence of the tetrakis(disubstituted-amino)ethylene. Suitablesolvents of this type include the hydrocarbons such as nhexane, decane,decalin, triisobutylene, cetane, tetra-isobutylene, n-octadecane,l-octadecene, purified kerosenes, white gasolines, or the more viscoushydrocarbons such as mineraloil and the like, or solid or semisolidhydrocarbons such as paraffin wax; nonquenching synthetic oils such assilicone oils, polyalkylene glycols, and diesters; nonquenching,preferably essentially hydrocarbon esters such as ethyl acetate;nonquenching hydrocarbon ethers such as tetrahydrofuran, diethyl ether,dimethyl ether, and the like.

The oxyluminescent compositions can also include compatiblenonquenching, organic or inorganic, thickening agents. Examples ofsuitable nonquenching thickening agents include nonreducible,noncoordinating inorganic oxides, preferably in colloidal dispersion,such as silica, alumina, zinc oxide, and the like; organic nonquenchingpolymers such as the hydrocarbon polymers, cg, polyisobutylene,polypropylene, polyethylene, and the like; nonquenching polyesters,e.g., polyvinyl acetate and the like; nonquenching polyethers such aspolytetramethylene oxide and the like; nonquenching olefin/ estercopolymers such as ethylene/vinyl acetate copolymers and the like.

A wide variety of porous substrates can be used in the articles of thisinvention for absorbing the oxyluminescent material. Among those thatare useful are foamed or otherwise cellular sheets, ribbons, strands orropes of polymers such as polystyrene, polyurethanes, poly(vinylchloride), polyethylene, and polyacrylonitrile; glass fiber fabric (bothwoven and nonwoven); cellulos'ic paper such as bleached kraft paper orsulfite paper; fabrics (both woven and nonwoven) of such fibers aspoly(ethylene terephthalate) fiber, rayon, cotton, nylon and acrylicfibers; mats or fabrics made of porous poly (vinylidene chloride) fibersand vinyl chloride copolymers; sheets made of opaque, foamed plasticfibers; sheets of alkali cellulose; nonwoven sheets of polyethylene orpolypropylene fibers; and glass fiber sheets, paper, and mats.

The flexible plastic envelopes of the panels and the plastic tubes canalso be made of a wide variety of polymeric materials. For example, theplastic layer surrounding the oxyluminescen-t impregnated poroussubstrate can be made of polyolefins, e.g., polyethylene; fiuorinatedpolymers; polyacrylonitrile; polyesters, e.g., poly(ethyleneterephthalate); polyamides; polyvinyl alcohol; poly(vinyl fluoride);poly(vinyl chloride); cellulosic films; laminations of two or moresheets of different polymers, e.g., polyethylene and poly(ethyleneterephthalate) films; and the like. The plastic envelopes and tubes canalso be coated with coating compounds, such as poly(vinylidenechloride), to impart certain desired properties to the envelope, e.g.,low oxygen permeability, heat sealability, or an adhesive surface.

As indicated above, spacers positioned between the porous substrate andthe enclosing envelope or tube provide more uniform and more intenselight emission from the oxyluminescent layer. These spacers can be madeof any inert, nonquenching material that can be fabricated in anopen-mesh or net-like structure. Examples of specific spacers that aresatisfactory include polyethylene netting, polypropylene netting,cheesecloth, nylon scrim, nylon netting, loosely woven glass fiberfabric, and the like.'No spacer is needed with porous substrates thathave a rough or uneven surface that permits good air circulation.

The oxyluminescent articles of this invention are illustrated in furtherdetail in the following examples.

Example 1 Sheets of the following porous materials are sealed inpolyethylene pouches and alternately flushed with nitrogen and evacuatedseveral times:

(1) Foamed polystyrene (2) Foamed polyurethane (3) Glass fiber filtermat Into each pouch there is then introduced by hypodermic needle 480ml. per square foot of porous sheet of a 50% by volume solution oftetrakis(dimethylamino)ethylene in mineral oil. The panels thus preparedluminesce briefly by interaction with small amounts of oxygen stillpresent. The polyurethane foam panel is yellower than the others. Afterthree days storage in air at room temperature, no light emission isobserved in a partly darkened room, but there is a liquid layer, atleast part of which is exudate, on the outside of each panel. When asmall amount of air is pumped into the panels, all three luminesce andthe one with polyurethane foazn is yellower, as before. After four daysfurther storage in air at room temperature, much more liquid hascollected on the outside of the panels, at least part of the liquidbeing exudate. When air is pumped in, the panel containing the glassfiber mat glows very strongly, the one containing the polyurethane foamglows moderately, and the one with polystyrene foam luminesces faintly.

Example II A panel is prepared using a piece of unsized bleached kraftpaper about inch thick as the absorbent porous layer. The porous layeris placed between sheets of poly (ethylene terephthalate) film which arethen sealed at the edges with a polyurethane cemeiit. The panel isevacuated and flushed with nitrogen through a hypodermic needle andthere is added 22 ml. of tetrakis(dimethylamino)ethylene per square footof the kraft paper by means of a hypodermic needle. After removal of theneedle, the hole remaining in the outer envelope is sealed with tape.After 20 days storage in air at room temperature, the tape is removedfrom the hole left by the hypodermic needle and light emission from theoxyluminescent layer is observed. However, the light emission is patchyand nonuniform because the film in some areas clings to the wetsubstrate and prevents uniform contact of air with the oxyluminescentmaterial.

Example III Panels are prepared as described in the preceding exampleexcept that the porous substrate in one panel is 1.5 g. of apoly(ethylene terephthalate) fiber nonwoven mat containing about 10% ofa polymeric binder and in a second panel is 2.2 of a semidullpoly(ethylene terephthalate) fiber fabric. In both cases, the outerenvelope is a composite consisting of polyethylene film laminated withpoly(ethylene terephthalate) film. The polyethylene layer is placedtoward the inside of the envelope to permit heat sealing. The edges ofthe panels are heat sealed and then both panels are evacuated andflushed with nitrogen. There are than added to the panels 4.4 and 4.0ml., respectively, of tetrakis(dimethylamino)- ethylene by a hypodermicneedle. The holes left by the needle are sealed by tape. After 2 weeksstorage in air at room temperature, the polyethylene layers in bothpanels are swollen and the laminations are separated. However, thepanels still remain sealed. After storage for six months in air at roomtemperature, the panel having the nonwoven polyester mat displays goodlight emission when air is admitted.

Example IV A panel is prepared as described in Example II except thatthe porous substrate is a glass fiber mat having a polyester binder. Theouter envelope is a laminate of polyethylene and poly(ethyleneterephthalate) with the edges sealed by heat. The panel is stored forfive months in air at room temperature and then air is admitted,whereupon the panel emits light.

Example V A panel is prepared as described in Example H with theexception that the porous substrate is 2.3 g. of a glass fiber mat about4-5 inches square. The mat is enclosed in a pouch of polyethylene film3.5 mils thick. The panel glows quite strongly after approximately 2.3ml. of tetrakis(dimethylamino)ethylene is added. At the end of twohours, a low-to-medium glow is readily visible in a partly darkenedroom. After nine hours, the panel can be seen easily outside after darkat a distance of feet, even with a lighted home nearby. The lightemission is maintained by air diffusing through the polyethyleneenvelope. The panel continues to glow for at least three days, althoughthe glow is quite feeble by the third day. The panel becomes oily on theoutside as tetrakis(dimethylamino)ethylene and/or its oxidation productsdiffuse through the polyethylene envelope.

A panel prepared as described in the immediately preceding paragraph,but with the outer envelope constructed of polyethylene of 1 milthickness, glows strongly after the tetrakis(dimethylamino)ethylene isadded. The light emission continues at a much higher level than in thecase of the panel made with 3.5 mil polyethylene because of the morerapid diffusion of air through the thinner polyethylene envelope. Theglow becomes relatively feeble after about five hours.

7 Example VI Open-end pouches about inches square are prepared by heatsealing three edges of two sheets consisting of polyethylene, 2 milsthick, laminated to poly(ethylene terephthalate) film. A poroussubstrate consisting of 0.53 g. of nonwoven poly(ethylene terephthalate)fabric is placed in the pouch and then 0.47 g. of glass fiber isinserted uniformly between the porous substrate and the outer envelopeto serve as a spacer between the substrate and the outer envelope. Thepouch is sealed, and air in it is replaced with nitrogen by evacuatingand adding nitrogen with the aid of a hypodermic needle. Approximately 4m1. of tetrakis(dimethylamino)ethylene is then 8 Example IX Two panelsare prepared and tested as in Example VIII except that nylon netting isused as the spacer between the porous layer and the envelope, and alayer of aluminum foil is cemented to the back of one of the panels. Airis admitted and the light emission is measured with a photographicexposure meter in which the clear window of the meter is fitted withcolored glass filters (Corning filters Nos. 375 and 468) so that themeter has the same spectral sensitivity as the dark-adapted eye. Inaddition, the modified meter is calibrated so that the brightness of thepanels can be measured in food lamberts.

BRIGHTNESS, IN FOOT LAMBERTS added by means of a hypodermic needle, andthe hole left by the needle is closed by means of tape. After severalhours, the envelope is opened by removing the tape over the hole and thepanel is worked by hand to introduce air. The substrate glows with abright, blue-white light. The glow is brightest where the glass fibershold the outer envelope away from the substrate. After one hour, therestill remains light around the hole over onehalf of the area. The panelis again worked by hand. After another hour, the light emission issimilar to that of the preceding hour. The hole in the bag is rescaledand the light emission soon ceases.

Example VII Three panels are prepared as described in Example II using5" x 5" pieces of glass fibed paper weighing about 1.2 g. each as theporous substrate and a poly (ethylene terephthalate)/polyethylenelaminated film as the outer envelope. The substrates are impregnatedunder nitrogen with about 3.5 ml., respectively, oftetrakis(dimethylamino)ethylene, a 50%, by volume, solution oftetrakis(dimethylamino)ethylene in mineral oil, and a composition madeup of 100 ml. of tetrakis(dimethylamino)ethylene, 100 ml. of technicaldecane, 5 ml. of adiponit-rile, and 2 g. of high molecular weightpolyisobutylene. When air is admitted to the panels and the lightemitted is measured with a photometer, the brightness of the panels isfound to be 2.8, 4.4, and 1.9 foot lamberts, respectively.

Example VIII A panel is prepared in the usual way using glass fiberpaper as the porous substrate and poly(ethyleneterephthalate)/polyethylene laminated film as the envelope. To preventthe film from adhering to the impregnated substrate, a layer ofpolypropylene netting is placed on the topside of the glass fiber paperbefore scaling in the envelope. The porous paper (0.9 g., 4.2" x 5") isimpregnated under nitrogen with 4.4 ml. of a 50%, by volume, solution oftetrakis(dimethyl-amino)ethylene in mineral oil. Air is admitted to thepanel at a controlled rate of 2 ml. per minute While the light emissionfrom the panel is measured at a distance of about 3" with a highlysensitive photographic exposure meter The following meter readings areobserved:

Meter Time: Reading 0 min 7.5

min 8.2

30 min 8.0

60 min 6.5

2 hrs. 4.7

These results show the effectiveness of the aluminum foil backing inincreasing the front light emission of the tetrakis dimethylaminoethylene-impregnated panel.

Example X An aluminum foil-backed panel four feet square is prepared asdescribed in Example IX with the exception that two ports ofpolyethylene tubing flanged at the bottom are heat sealed in to the toplayer of the envelope of poly(ethylene terephthalate)/polyethylenlaminate near two opposing corners. These ports are used for flushingthe panel with nitrogen and for adding 450 ml. of a 50%, by volume,solution of tetr-akis(dimethylamino) ethylene in mineral oil. The panelis attached to a frame and held in a vertical position about six feetoff the ground on a relatively clear night (but with the moon obscuredby clouds) at 30 F. Air is introduced by mouth to the panel andobservers two miles away are able to see the panel easily, due to theluminescence of the impregnated layer. There is no difliculty in readingprinted matter at a distance of 15 feet by means of the light emittedfrom the panel. After one hour, durin which no further air isintroduced, the panel is still visible to the observers two miles away.

Example XI A panel is prepared as in Example X with the exception thatthe clear plastic envelope is prepared from transparent, orientedpoly(vinyl fluoride) film 2 mils thick and no aluminum foil is attachedto the back. The panel is rolled up and sealed under nitrogen in a glasstube. The tube containing the panel is then stored in a room withnatural and artificial illumination. After storage for eight months, thetube is opened, aluminum foil is applied to the back of the panel, airis admitted, and the light emission from the panel is measured. Only asingle charge of air is introduced at the start of the test. Thefollowing results are obtained with the photographic exposure meter asmodified With colored filters (Example IX):

BRIGHTNESS OF PANELS AFTER EIGHT MONTHS STORAGE Brightness, in

These results show the good stability of the panel to long-term storage.

and light is again emitted when the valves are open for a short time.

When the procedure of Example XX is repeated with the exception that thesame cthylene/ ethyl acrylate copolymer tubing is used without anycoatings, the tubing is seen to glow dully when observed in a dark room.Thus, the uncoated ethylene/ ethyl acrylate tubing is permeable to airto some extent.

Example XXI A 3" length of inside diameter x /8 outside diameterpolypropylene tubing is flushed with nitrogen and then one-half filledwith the tetrakis(dimethylamino)- ethylene/mineral oil solution ofExample XVIII and the ends are closed with serum stoppers. When observedin a dark room, the tubing glows at a low level because of slowdiffusion of air through the walls of the tubing. After six Weeks, alittle air is injected into the tubing and considerable light emissionis observed in a darkened area.

In addition to the various embodiments. already mentioned in theexamples and in the general discussion of modifications and equivalents,the oxyluminescent articles of this invention can also include stillother modifications. For example, the shape of the panels can be variedfrom the flat, rectangular panels described in detail above to narrowribbon-like panels, and to panels of various shapes, such as domes,pyramids, and the like. These various shapes can be achieved duringinflation of the panel with air or oxygen or by means of ribs, staves,or air-inflatable channels built into the panels.

In another embodiment, the articles can be constructed dry, i.e.,without the active oxyluminescent material being impregnated in theporous substrate, and the panels or tubes fitted with pressurizedcontainers filled with the active oxyluminescent composition fordischarge into the inside of the article when desired.

In still another embodiment, the articles can :be fitted withpressurized containers filled with air or oxygen or a mixture of oxygenwith a gas that is inert to the oxyluminescent material for dischargeinto the center of the article when light emission is desired.

The valve for admitting air or oxygen to the inside of the article can,if desired, be fitted with a chamber containing a drying agent, e.g.,anhydrous calcium chloride, so that the air or other gas admitted to theinterior will be dry. This embodiment is advantageous when theoxyluminescent material is decomposed or sensitized by moisture.

In addition to the incorporation of oils, waxes, and

various organic and inorganic thickening agents to control the viscosityof the oxyluminescent material as described previously, theoxyluminescent material can also be compounded with colorants of varioustypes, e.g., dyes and pigments, to modify the color of the light emittedby the article. A colored filter, e.g., a dyed or pigmented film, canalso be used to modify the color of the emitted light.

In still another embodiment, the articles of this invention can befitted with containers of a quenching agent for discharge into the panelor tube when it is desired to stop the light emission. Examples ofsuitable quenching agents for this use include acetone, cyclohexanone,tetrachloroethylene, nitrobenzene, and the like.

As indicated previously, the extended light sources of this inventionare useful in many applications. More particularly, the oxyluminescentpanels and tubes are highly suitable for use in rescuing crew membersand passengers of aircraft which have been downed in remoteuninhabitated places on land or sea. The tubular light sources andnarrow ribbon-like panels are especially suitable for the emergencylighting of life rafts, life vests, aircraft escape slides, aircraftinstrument panels, and other locations in the interior of aircraft. Theflexibility of the tubing and ribbon enables emergency equipment towhich they are attached to be folded up for storage until needed inemergencies. The oxyluminescent articles carried by the aircraft in aninactive state can be activated rapidly when needed to signal rescuersat night.

The foregoing detailed description has been given for clearness ofunderstanding only and no unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed, for obvious modifications will occur to those skilled in theart.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. An oxyluminescent article comprising a plastic enclosure containing aporous substrate impregnated with atetrakis(disubstituted-amino)ethylene oxyluminescent material, saidenclosure being provided with means for admitting air in controllableamounts, and being further characterized by having at least one areawhich permits the passage of light.

2. An oxyluminescent article comprising a sheet-like porous substrateimpregnated with a tetrakis (disubstitutcdamino)ethylene oxyluminescentmaterial enclosed in a flexible plastic envelope, at least one portionof which permits the passage of light through it, said envelope beingfitted with at least one means for admitting air in controllable amountsto the oxyluminescent material.

3. An oxyluminescent article comprising a rope-like porous substrateimpregnated with a tetrakis(disubstitutedamino)ethylene oxyluminescentmaterial enclosed in a plastic tube, at least one portion of whichpermits the passage of light through it, said tube being fitted with atleast one means for admitting air in controllable amounts to theoxyluminescent material.

4. An article of claim 1 where the enclosure is a tough plastic havinglow oxygen permeability and high resistance to the oxyluminescentmaterial and its oxidation products.

5. Articles of claim 1 Where the porous substrate is provided with acoarse, open-mesh, net-like structure to prevent intimate contact withthe enclosure.

6. Articles of claim 2 wherein the side of the plastic envelope oppositethe translucent or transparent area is provided with a light-reflectivelayer.

7. Articles of claim 3 wherein the tube is provided with a lightreflector Whose cross section is flat, he-micylindrical or parabolic.

8. Articles of claim 1 where the oxyluminescent material is atetrakis(disubstituted-amino)ethylene of the formula wherein the R's,which need not be the same, are selected from the group consisting ofmonovalent alkyl of up to 10 carbons, monovalent cycloalkyl of up to 10carbons, divalent alkylene joined to the other R attached to the samenitrogen to form a 3-5 membered monoaza heterocycle, and divalentalkylene joined to an R attached to a second nitrogen to form a 3-7membered diaza heterocycle.

9. Articles of claim 1 wherein the oxyluminescent material is in aninert carrier.

10. Articles of claim 1 in the form of panels in which the backs arecoated with a pressure-sensitive adhesive.

11. Articles of claim 1 in which the porous substrate is colored.

12. An oxyluminescent panel comprising a porous substrate of glass fiberpaper impregnated with tetrakis- (dimethylamino)ethylene enclosed in atransparent envelope of polyethylene terephthalate/polyethylenelaminated film, said substrate being kept out of intimate contact withthe enclosing envelope by means of a spacer of nylon netting, saidenvelope being fiitted with a port for controlled admission of air andhaving attached to the outside of one side a light-reflective layer ofaluminum foil.

13. An oxyluminescent panel comprising a porous substrate of nonwovenpolyethylene terephthalate fabric 9 Example XII A panel is prepared inthe usual way using glass fiber paper as the porous substrate, nylonnetting as the spacer, poly(vinyl fluoride) film as the envelope, andaluminum foil backing. The panel is flushed with nitrogen and the porouslayer is impregnated with 4 ml. per square decimeter of a compositioncomprising 15 volumes of mineral oil and 9 volumes of1,1',3,3'-tetraethyl-A bi(imidazolidine). Air is admitted to the paneland light emission is observed. A brightness of 0.1 foot lambert isindicated by a sensitive photographic exposure meter within 15 secondsafter the air is admitted.

Example XIII Two panels are prepared as in Example XII except that inone case a layer of poly(ethylene terephthalate) cloth dyed red with adye (Colour Index No. C. I. Basic Red 15) is placed between the glassfiber paper and the nylon net and in the other case three layers of thedyed fabric are substiuted for the glass paper. The panels are flushedwith nitrogen and the substrates are impregnated with 4 ml. per squaredecimeter of a 37%, by volume, solution oftetrakis(dimethylamino)ethylene in mineral oil. When air is admitted,the panels emit red light instead of the blue-green light seen in thepanels described in Examples IXII. A brightness of at least 0.2 footlambert is recorded by a sensitive photographic exposure meter.

Example XIV Two panels are prepared as in Example XIII except that theporous substrates are pigmented polypropylene felts. The felts areimpregnated with dispersions of fluorescent pigment, prepared byencasing fluorescent dyes in an insoluble polymeric matrix and grinding,in aqueous polyvinyl alcohol solution. For one panel the fluorescentpigment is one known commercially as Day Glo Fluorescent Pigment SaturnYellow T17, and for the other it is Fire Orange T14. The panels areflushed with nitrogen and the felts are impregnated with 6.7 ml. persquare decimeter of a 37%, by volume, solution oftetrakis(dimethylamino)ethylene in mineral oil. Air is admitted and thepanels are seen to emit yellow and red light, respectively. Thebrightness of the yellow panel five minutes after the air is admitted is5 foot lamberts and that of the red panel is 0.9 foot lambert.

Example XV A panel is prepared as described in Example IV with theexception that the porous susbtrate is a sheet of alkali cellulose. Whenair is admitted the panel glows quite strongly. However, the browndiscoloration usually noted during prolonged oxidation and lightemission is absent, due to presence of the alkali in the alkalicellulose porous substrate.

The beneficial effect of alkali in enhancing the oxyluminescence oftetrakis(disubstituted-amino)ethylene compositions and in preventingdiscoloration of such compositions as demonstrated by Example XV is alsosupported by the following observations: (1) When a layer oftetrakis(dimethylamino)ethylene is exposed to air while floating onaqueous solutions containing 8% borax, 10% sodium borohydride (whichsoon decomposes to sodium borate and hydrogen), potassium hydroxide, 10%disodium dodecahydrododecaborate and 5% disodium dodecahydrododecaboratel-5% sodium peroxide (which decomposes to sodium hydroxide and oxygen),1.5, 2.5, 3.0, 3.5, and 5.3 times, respectively, as much light isgenerated as when a layer of the peraminoethylene is exposed to air onwater alone. (2) Furthermore, tetrakis(dimethylamino)ethylene in contactwith water or alcohol, especially in the presence of a little air,produces a deep yellow or brown discoloration in the water or alcoholand also produces free radicals as indicated by electron paramagneticresonance measurements; whereas this peraminoethylene in contact withalkali solu- 10 tions produces neither color nor an electronparamagnetic resonance signal.

Example XVI An approximately one-foot length of A nominal diameterpolyvinyl alcohol tubing is partially filled with an 11" length ofuntreated electrical grade A", nominal flat width, glass cloth sleeving.The partly filled tubing is flushed with nitrogen and the ends areclosed with serum stoppers. By means of a hypodermic syringe and needle,sufficient tetrakis(dimethylamino)ethylene is injected to saturate theglass cloth. Three hours later no light emission from the tubing can bedetected in a dark room, even after five minutes of dark adaptation.However, when a little air is injected into the tubing, considerablelight is emitted and the whole tube glows. After standing one month, thetube glows anew when additional air is injected.

Example XVII Another polyvinyl alcohol tube is prepared as in ExampleXVI except that the glass cloth is saturated with a 37%, by volume,solution of the peraminoethylene in mineral oil. When air is injectedinto the tubing, the tube glows and may be seen easily from a distanceof feet in a semidark residential area.

Example XVIII An approximately one-foot length of tubing made of acopolymer of tetrafluoroethylene and hexafluoropropylene having W insidediameter and 25 mil wall thickness is loaded with glass cloth as inExample XVI and the cloth is saturated under nitrogen with a 20/34(volume/ volume) solution of tetrakis(dimethylamino)ethylene/ mineraloil. After standing for one day, the tubing can be seen to be glowingslightly when examined in a dark room. This slight glow is due to slowpermeation of air through the wall of the tubing. The tubing glowsstrongly when air is injected into it.

Example XIX A 3 length of /8 outside diameter, 32 mil wall thicknessnylon tubing is loaded with glass cloth as in Example XVI and the clothis saturated under nitrogen with thetetrakisQdimethylamino)ethylene/mineral oil solution of Example XVIII.After standing for two days, the tubing and its contents appearunchanged. In a dark room the tubing exhibits a very dull glow,indicating a very slow but finite permeation of air through the tubingwall. A bright emission of light is seen when air is injected into thetubing. After standing for 19 Weeks, a little air is injected and thetubing is seen to emit considerable light.

Example XX A 30" length of inside diameter, /1" outside diameterethylene/ethyl acrylate copolymer tubing is dipped in succession into 1,l, and 15 methyl ethyl ketone solutions, respectively, of (a)tetraisopropyl titanate, (b) a terpolymer of 86% vinyl chloride, 11%vinyl acetate, and 3% maleic anhydride, and (c) a copolymer of 60%vinylidene chloride and 40% vinyl chloride. After each dip, the tubingis allowed to dry and is baked five minutes at 82 C. The tubing isfilled with six 26" lengths of M2" wide electrical grade glass clothsleeving having no finish and weighing 11 g. The tubing is flushed withnitrogen, the glass cloth is saturated with 11 ml. of thetetrakis(dimethylamino)ethylene/mineral oil solution of Example XVIIIand ends are closed with metal valves. Essentially no light emission isobserved when the tubing is exposed in a dark room. When the valves areopened for a short time and air is admitted or deliberately forced intoand through the tubing, the tubing glows and emits light for some time.This process can be repeated many times. After standing five weeks, thetubing still has the light yellow appearance that it had when firstprepared impregnated with tetrakis (dimethylamino)ethylene enclosed in atransparent envelope of poly(v'myl fluoride) film, said substrate beingkept out of intimate contact with the enclosing envelope by means of aspacer of polypropylene netting, said envelope being fitted with a portfor controlled admission of air and having attached to the outside ofone side a light-reflective layer of aluminum foil.

14. An oxyluminescent tube comprising a porous substrate of glass clothsleevin-g impregnated with tetrakis- (dimethylamino)ethylene enclosed ina tube of polyvinyl alcohol, said tube being fitted with means forcontrolled admission of air.

15. An oxyluminescent tube comprising a porous substrate of glass clot-hsleeving impregnated with tetrakis- (dimethylamino)ethylene enclosed ina tube of a copolymer of tetrafiuoroethylene and hexafluoropropylene,said tube being fitted with means for controlled admission of air.

16. Process for preparing oxyluminescent panel-type articles whichcomprises placing a layer of a porous substrate that is inert totetrakis(disubstituted-amino)- ethylenes between two sheets of flexibleplastic, at least one of which permits passage of light through it, of asize larger than said substrate, inserting through an opening made nearthe edge of one sheet means for permitting access to the envelope formedby sealing the edges of the plastic sheets, sealing said edges,replacing the air in the interior of the envelope with an inert gas, andintroducing a tetrakis(disubstituted-amino)ethylene as theoXyluminescent material via said means into the interior of theenvelope, thereby completing impregnation of the porous substrate withthe oxylumine-scent material under substantially oxygen-free conditions.

17. Process for preparing oxyluminescent tubular articles whichcomprises passing a cord through a length of plastic tubing, at least aportion of said tubing being such as to permit passage of light throughit, attaching one end of the cord to the end of a sleeving of a poroussubstrate that is inert to tetrakis(disubstituted-amino)- ethylenes,pulling the porous substrate into the tube, the cross secional area ofthe substrate being such that it does not completely fill the tube,closing the ends of the tube, inserting means for permitting access tothe inner portion of the tube, replacing the air in the inner portion ofthe tube with an inert gas, and introducing a tetrakis(disubstituted-amino)ethylene as the oXyluminescent material via said meansinto the inner portion of the tube, thereby completing impregnation ofthe porous substrate with the oxyluminescent material undersubstantially oxygen-free conditions.

18. In the process of claim 16, the step of inserting a coarse,open-mesh structure between the porous substrate and the plastic sheetwhich permits the passage of light, said structure serving as a spacerto prevent the substrate when wet with oxyluminescent material fromadhering to the outer plastic sheet.

References Cited UNITED STATES PATENTS 2,75 0,027 6/1956 Cummings.3,110,836 11/1-963 Blazek et al. 3,239,406 3/1966 Cofiman et a1. 25071 XL. DEWAYNE RUTLEDGE, Primary Examiner.

1. AN OXYLUMINESCENT ARTICLE COMPRISING A PLASTIC ENCLOSURE CONTAINING APOROUS SUBSTRATE IMPREGNATED WITH ATETRAKIS(DISSUBSTITUTED-AMINO)EHTYLENE OXYLUMNESCENT MATERIAL, SAIDENCLOSURE BEING PROVIDED WITH MEANS FOR ADMITTING AIR IN CONTROLLABLEAMOUNTS, AND BEING FURTHER CHARACTERIZED BY HAVING AT LEAST ONE AREAWHICH PERMITS THE PASSAGE OF LIGHT.